The one exception, intriguingly, was iPhone 1.0. It was way more stable than I expected.
iPhone 2.0 may represent a return to form:
Did Apple set developers up for failure? - The Unofficial Apple Weblog (TUAW)If you're not in a real rush, it would be good to wait until at least the next major firmware update before buying.
... Anonymous developer sources are reporting that they've been poring over crash logs and discovering that the reported crash has nothing to do with their application. There's a growing consensus that Apple has released a highly unstable 'final' version of the 2.0 firmware...
I'll be buying anyway, but I've already decided I won't be able to abandon my Palm for another 6-12 months due to other iPhone limitations. So I'll be ok with a crashy device.
They'll fix it, probably faster than Apple fixed 10.5 (that took over a year).